Sources, meanwhile, tell ESPN's Ramona Shelburne that negotiations are ongoing and Ballmer's bid has not been proclaimed the winner yet. Banned owner Donald Sterling's lawyer tells ESPN that his client has not signed off on any sale and would need to do so before a bid could be accepted.

Sterling's wife, Shelly, has pushed to negotiate a sale before Tuesday's board of governors meeting at which both of the Sterlings' ownership interests could be terminated, while Donald Sterling has vowed to fight the NBA's attempts to force a sale.

The $2 billion price tag would be the second-most ever for a North American professional sports franchise. The Los Angeles Dodgers were sold in 2012 for $2.1 billion. It would be the most paid by far for an NBA team, after the $550 million paid for the Milwaukee Bucks this year.

Ballmer, 58, was CEO of Microsoft from 2000 to '14, and reportedly is worth $20 billion. He was the only investor that did not immediately seek out other partners when preparing a bid.

On Wednesday, Seattle Seahawks (and former USC Trojans) coach Pete Carroll took to Twitter to back Ballmer.

The Clippers would be so fortunate to get Steve Ballmer as owner. He's a great competitive force & would bring big energy to the LAC fanbase

It's not the first time Ballmer has bid on an NBA team. He was part of a group that attempted to buy the Sacramento Kings last year, with the intent of moving the team to Seattle. NBA owners voted to reject the proposed move.

Ballmer told The Wall Street Journal earlier this month that, should he obtain the Clippers, he would not attempt to move the franchise from Los Angeles, saying that would be "value destructive."

Shelly Sterling told bidders to submit letters of interest by Wednesday, with firm offers due by 5 p.m. ET on Thursday.